public abstract class AbstractMap extends java.lang.Object implements Map, Rollbackable
entrySet
(usually via an
AbstractSet). To make it modifiable, also implement put
,
and have entrySet().iterator()
support remove
.
It is recommended that classes which extend this support at least the no-argument constructor, and a constructor which accepts another Map. Further methods in this class may be overridden if you have a more efficient implementation.
Map
,
Collection
,
HashMap
,
LinkedHashMap
,
TreeMap
,
WeakHashMap
,
IdentityHashMap
Modifier and Type | Field and Description |
---|---|
protected Checkpoint |
$CHECKPOINT |
protected CheckpointRecord |
$RECORD$$CHECKPOINT |
Modifier | Constructor and Description |
---|---|
protected |
AbstractMap()
The main constructor, for use by subclasses.
|
Modifier and Type | Method and Description |
---|---|
void |
$COMMIT(long timestamp)
Commit changes up to the given timestamp, but not including changes
made at timestamp and afterward.
|
Checkpoint |
$GET$CHECKPOINT()
Get the checkpoint object that monitors this rollbackable object.
|
void |
$RESTORE(long timestamp,
boolean trim)
Restore a previous state to all the private fields of this rollbackable
object.
|
java.lang.Object |
$SET$CHECKPOINT(Checkpoint checkpoint)
Set the checkpoint object of this rollbackable object.
|
void |
clear()
Remove all entries from this Map (optional operation).
|
protected java.lang.Object |
clone()
Create a shallow copy of this Map, no keys or values are copied.
|
boolean |
containsKey(java.lang.Object key)
Returns true if this contains a mapping for the given key.
|
boolean |
containsValue(java.lang.Object value)
Returns true if this contains at least one mapping with the given value.
|
abstract Set |
entrySet()
Returns a set view of the mappings in this Map.
|
boolean |
equals(java.lang.Object o)
Compares the specified object with this map for equality.
|
java.lang.Object |
get(java.lang.Object key)
Returns the value mapped by the given key.
|
int |
hashCode()
Returns the hash code for this map.
|
boolean |
isEmpty()
Returns true if the map contains no mappings.
|
Set |
keySet()
Returns a set view of this map's keys.
|
java.lang.Object |
put(java.lang.Object key,
java.lang.Object value)
Associates the given key to the given value (optional operation).
|
void |
putAll(Map m)
Copies all entries of the given map to this one (optional operation).
|
java.lang.Object |
remove(java.lang.Object key)
Removes the mapping for this key if present (optional operation).
|
int |
size()
Returns the number of key-value mappings in the map.
|
java.lang.String |
toString()
Returns a String representation of this map.
|
Collection |
values()
Returns a collection or bag view of this map's values.
|
protected transient Checkpoint $CHECKPOINT
protected transient CheckpointRecord $RECORD$$CHECKPOINT
public abstract Set entrySet()
Iterator.remove
, Set.remove
,
removeAll
, retainAll
, and clear
.
Element addition is not supported via this set.public void clear()
AbstractMap.clear
unless you want an infinite loop.clear
in interface Map
java.lang.UnsupportedOperationException
- if entrySet().clear()
does not support clearing.Set.clear()
protected java.lang.Object clone() throws java.lang.CloneNotSupportedException
super.clone()
.clone
in class java.lang.Object
java.lang.CloneNotSupportedException
- if a subclass is not CloneableCloneable
,
Object.clone()
public boolean containsKey(java.lang.Object key)
entrySet()
, returning true
if a match
is found, false
if the iteration ends. Many subclasses
can implement this more efficiently.containsKey
in interface Map
key
- the key to search forjava.lang.NullPointerException
- if key is null
but the map
does not permit null keyscontainsValue(Object)
public boolean containsValue(java.lang.Object value)
entrySet()
, returning true
if a match
is found, false
if the iteration ends. A match is
defined as a value, v, where (value == null ? v == null :
value.equals(v))
. Subclasses are unlikely to implement
this more efficiently.containsValue
in interface Map
value
- the value to search forcontainsKey(Object)
public boolean equals(java.lang.Object o)
true
if the other object is a Map with the same mappings,
that is,o instanceof Map && entrySet().equals(((Map) o).entrySet();
equals
in interface Map
equals
in class java.lang.Object
o
- the object to be comparedSet.equals(Object)
public java.lang.Object get(java.lang.Object key)
null
if
there is no mapping. However, in Maps that accept null values, you
must rely on containsKey
to determine if a mapping exists.
This iteration takes linear time, searching entrySet().iterator() of
the key. Many implementations override this method.get
in interface Map
key
- the key to look upjava.lang.NullPointerException
- if this map does not accept null keyscontainsKey(Object)
public int hashCode()
hashCode
in interface Map
hashCode
in class java.lang.Object
Map.Entry.hashCode()
,
Set.hashCode()
public boolean isEmpty()
size() == 0
.public Set keySet()
This implementation creates an AbstractSet, where the iterator wraps the entrySet iterator, size defers to the Map's size, and contains defers to the Map's containsKey. The set is created on first use, and returned on subsequent uses, although since no synchronization occurs, there is a slight possibility of creating two sets.
keySet
in interface Map
Set.iterator()
,
size()
,
containsKey(Object)
,
values()
public java.lang.Object put(java.lang.Object key, java.lang.Object value)
null
values, a null return does not always
imply that the mapping was created.put
in interface Map
key
- the key to mapvalue
- the value to be mappedjava.lang.UnsupportedOperationException
- if the operation is not supportedjava.lang.ClassCastException
- if the key or value is of the wrong typejava.lang.IllegalArgumentException
- if something about this key or value
prevents it from existing in this mapjava.lang.NullPointerException
- if the map forbids null keys or valuescontainsKey(Object)
public void putAll(Map m)
put
,
so it is not supported if puts are not.putAll
in interface Map
m
- the mapping to load into this mapjava.lang.UnsupportedOperationException
- if the operation is not supported
by this map.java.lang.ClassCastException
- if a key or value is of the wrong type for
adding to this map.java.lang.IllegalArgumentException
- if something about a key or value
prevents it from existing in this map.java.lang.NullPointerException
- if the map forbids null keys or values.java.lang.NullPointerException
- if m
is null.put(Object, Object)
public java.lang.Object remove(java.lang.Object key)
remove
method.
It returns the result of getValue()
on the entry, if found,
or null if no entry is found. Note that maps which permit null values
may also return null if the key was removed. If the entrySet does not
support removal, this will also fail. This is O(n), so many
implementations override it for efficiency.remove
in interface Map
key
- the key to removejava.lang.UnsupportedOperationException
- if deletion is unsupportedIterator.remove()
public int size()
entrySet().size()
.size
in interface Map
Set.size()
public java.lang.String toString()
getKey() + "=" + getValue()
), separated by a comma and
space (", "), and surrounded by braces ('{' and '}'). This implementation
uses a StringBuffer and iterates over the entrySet to build the String.
Note that this can fail with an exception if underlying keys or
values complete abruptly in toString().toString
in class java.lang.Object
public Collection values()
This implementation creates an AbstractCollection, where the iterator wraps the entrySet iterator, size defers to the Map's size, and contains defers to the Map's containsValue. The collection is created on first use, and returned on subsequent uses, although since no synchronization occurs, there is a slight possibility of creating two collections.
values
in interface Map
Collection.iterator()
,
size()
,
containsValue(Object)
,
keySet()
public void $COMMIT(long timestamp)
Rollbackable
$COMMIT
in interface Rollbackable
$COMMIT
in interface Map
timestamp
- The timestamp.public void $RESTORE(long timestamp, boolean trim)
Rollbackable
$RESTORE
in interface Rollbackable
$RESTORE
in interface Map
timestamp
- The timestamp taken at the time when the previous
state was recorded.trim
- Whether to delete the records used for the rollback.Checkpoint.rollback(long, boolean)
public final Checkpoint $GET$CHECKPOINT()
Rollbackable
$GET$CHECKPOINT
in interface Rollbackable
$GET$CHECKPOINT
in interface Map
public final java.lang.Object $SET$CHECKPOINT(Checkpoint checkpoint)
Rollbackable
$SET$CHECKPOINT
in interface Rollbackable
$SET$CHECKPOINT
in interface Map
checkpoint
- The new checkpoint object.Checkpoint.setCheckpoint(Checkpoint)